857
FXUS61 KBOX 120601
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
201 AM EDT Tue May 12 2026

.WHAT HAS CHANGED...
No significant changes.

&&

.KEY MESSAGES...

- Dry and seasonably cool conditions through the first half of
  Wednesday.

- Unsettled midweek pattern with increasing chances for
  beneficial rainfall.

- Warm and mainly dry weekend pattern, but details remain
  uncertain.

&&

.DISCUSSION...
KEY MESSAGE 1...Dry and seasonably cool conditions through the first
half of Wednesday.

An amplified mid-level trough and embedded shortwave cross southern
New England early this morning. Outside of an isolated brief shower,
impacts are limited to increased cloud cover. Clearing develops
first across northwestern Massachusetts, where light winds support
radiational cooling. Lows fall into the mid 30s in the coldest
spots, with patchy frost possible. Most locations bottom out in the
upper 30s to lower 40s. The trough shifts offshore today, yielding
fair-weather cu and abundant sunshine. Despite sunshine, cool
conditions persist with 850mb temps near -1C to +1C, supporting
highs in the upper 50s to mid 60s. A weak pressure gradient brings
uncertainty to sea breeze development across eastern Massachusetts.
Otherwise, NW winds remain around 8 to 12 mph with generally quiet
conditions expected. CU diminishes this evening, followed by
increasing clouds overnight ahead of the next system. Cloud cover
will limit radiational cooling, with lows Wednesday morning mainly
in the 40s. Dry weather persists for many through at least the first
half of Wednesday as high pressure shifts offshore and low pressure
develops over the eastern Great Lakes.

KEY MESSAGE 2...Unsettled midweek pattern with increasing chances
for beneficial rainfall.

High pressure shifts east Wednesday as the next system approaches
from the west. Flow turns SW, advecting higher moisture with PWATs
increasing to 0.8 to 1.0 inches across southern New England by late
morning. Latest guidance supports an earlier onset of precipitation,
generally mid to late morning, as a warm frontal zone lifts through
the region. Best forcing initially focuses across western MA and
northwest/north-central CT. After a possible relative decrease in
coverage during the afternoon, rain expands eastward late Wednesday
into Thursday (primarily after 00Z) as a longwave trough becomes cut
off over northern New England and southern Quebec before slowly
drifting southeast toward the region Friday. As the mid-level and
surface lows become vertically stacked, widespread unsettled
conditions persist through Thursday, with gradual improvement Friday
afternoon as high pressure builds in from the southwest and ridging
develops to the west. This system continues to favor beneficial
rainfall. Ensemble guidance shows moderate probabilities for 0.5"+
QPF, with ECMWF/CMC ensembles in the 70 to 90 percent range and GEFS
lower at 30 to 60 percent. Ensemble percentiles generally support
0.3 to 0.6 inches at the 25th percentile and 0.8 to 1.2 inches at
the 75th percentile. Temperatures remain below normal through the
period, with highs in the lower to mid 60s Wednesday through Friday.
If the cutoff exits faster, Friday could trend milder.

KEY MESSAGE 3...Warm and mainly dry weekend pattern, but details
remain uncertain.

Upper trough exits and heights rise into the weekend and early next
week, supporting above-normal temperatures with highs in the 70s,
possibly approaching 80 degrees in warmer locations. Confidence is
lower regarding timing and coverage of any precipitation due to
potential embedded shortwaves, but overall trends favor mainly dry
conditions with only low-probability scattered showers or
thunderstorms Saturday into Sunday. By Monday, an anomalous ridge
builds over the Northeast, supporting continued dry and warm
conditions into early next week.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
Forecaster Confidence Levels...

Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.

06Z TAF UPDATE:

Today and Tonight...High confidence.

VFR. NW winds 7 to 10 kt. Sea breeze remains possible for KBOS
around 15z to 16Z, though development may be limited if NW winds
remain slightly stronger. Winds become light WNW/W tonight.

Wednesday...High confidence.

VFR early. -SHRA possible across western terminals late morning.
Conditions trend MVFR west to east Wednesday evening with -RA.
Winds S 10 to 15 kt.

KBOS...Moderate confidence.

VFR. Sea breeze development possible after 15z to 16Z. Slightly
stronger NW flow may keep the sea breeze offshore or oscillating
near the coast during the afternoon.

KBDL...High confidence.

VFR.

Outlook /Wednesday Night through Saturday/...

Wednesday Night: Mainly VFR, with local IFR possible. Breezy.
Chance SHRA, patchy BR.

Thursday: Mainly MVFR, with local IFR possible. Breezy. SHRA,
slight chance TSRA, patchy BR.

Thursday Night: Mainly MVFR, with areas IFR possible. SHRA,
slight chance TSRA, patchy BR.

Friday: MVFR/IFR conditions possible. Chance SHRA.

Friday Night: Mainly VFR, with local MVFR possible.

Saturday: VFR. Breezy.

&&

.MARINE...
Forecaster Confidence Levels...

Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.

Today through Wednesday...High confidence.

Winds and seas remain below Small Craft Advisory criteria through
Tuesday night. NW winds 10 to 15 kt today and tonight, with possible
sea breeze development nearshore this afternoon. Seas 4 ft or less.
Winds shift S Wednesday, increasing to 15 to 20 kt with gusts 25+ kt
and seas building to 4 to 6 ft over southern waters. Small Craft
Advisory conditions likely Wednesday into Thursday.

Outlook /Wednesday Night through Saturday/...

Wednesday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Seas locally approaching 5 ft. Slight chance
of rain showers.

Thursday: Winds less than 25 kt. Areas of seas approaching
5 ft. Rain showers, patchy fog.

Thursday Night: Winds less than 25 kt. Areas of seas
approaching 5 ft. Rain showers, slight chance of thunderstorms,
patchy fog.

Friday: Winds less than 25 kt. Seas up to 5 ft. Chance of rain
showers.

Friday Night: Winds less than 25 kt. Seas up to 5 ft. Slight
chance of rain showers.

Saturday: Winds less than 25 kt. Seas up to 5 ft.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.

&&

$$
Dooley